<!DOCTYPE html>
<html lang="en">
<head>
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    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <style>
        body{
            margin:0
        }
        .box1{
            width:300px;
            height:300px;
            margin:100px;
            background-color: #333;
            overflow: hidden;
            position:relative;
        }
        .box2{
            width:200px;
            height:200px;
            margin:100px;
            background-color: #666;
            overflow: hidden;
            
        }
        .box3{
            width:100px;
            height:100px;
            margin:100px;
            background-color: #999;
        }
    </style>
    <input type="text" class="box"/>
    <script>
     
    </script>
</body>
</html>